As a result of small fault current, high level of noise and a large penetration of distributed generators (DG), in the neutral non-effectively grounded medium-voltage (MV) distribution networks, it ...is quite difficult to locate the faulted line section for single phase to ground faults. In this paper, using a technique based on synchronized measurements in distribution networks, a fault location method based on the analysis of the energy of the transient zero-sequence current in the selected frequency band (SFB) is proposed. The equivalent impedance of the distribution network with lateral branches is studied with an equivalent network, and the phase-frequency characteristics of the equivalent impedance are analyzed. The SFB, within which the transient energy of the faulty line section is larger than that of the healthy line sections is determined. A combined fault-section location criterion is proposed and the implementation scheme is illustrated with the distribution level phasor measurement units. Numerical simulations of the IEEE 34 node system and the field experiments of a 10kV distribution network validate the feasibility and effectiveness of the proposed method.
Abstract
We review the mathematical speed limits on quantum information processing in many-body systems. After the proof of the Lieb–Robinson Theorem in 1972, the past two decades have seen ...substantial developments in its application to other questions, such as the simulatability of quantum systems on classical or quantum computers, the generation of entanglement, and even the properties of ground states of gapped systems. Moreover, Lieb–Robinson bounds have been extended in non-trivial ways, to demonstrate speed limits in systems with power-law interactions or interacting bosons, and even to prove notions of locality that arise in cartoon models for quantum gravity with all-to-all interactions. We overview the progress which has occurred, highlight the most promising results and techniques, and discuss some central outstanding questions which remain open. To help bring newcomers to the field up to speed, we provide self-contained proofs of the field’s most essential results.
► The prepared MMIPs were investigated by SEM, FTIR, XRD and VSM. ► The MMIPs were used as a sorbent to recognize resveratrol in wine. ► High selectivity and good recoveries were obtained.
The ...magnetic molecularly imprinted polymers (MMIPs) for resveratrol were prepared by using surface molecular imprinting technique with a super paramagnetic core–shell nanoparticle as a supporter. Rhapontigenin, which is the analogues of resveratrol, was selected as dummy template molecules to avoid the leakage of trace amount of resveratrol. Acrylamide and ethylene glycol dimethacrylate were chosen as functional monomers and cross-linker, respectively. The obtained MMIPs were characterized by using scanning electron microscopy, Fourier transform infrared spectrum, X-ray diffraction and vibrating sample magnetometer. High performance liquid chromatography was used to analyze the target analytes. The resulting MMIPs exhibited high saturation magnetization of 53.14emug−1 leading to the fast separation. The adsorption test showed that the MMIPs had high adsorption capacity for resveratrol and contained homogeneous binding sites. The MMIPs were employed as adsorbent of solid phase extraction for determination of resveratrol in real wine samples, and the recoveries of spiked samples ranged from 79.3% to 90.6% with the limit of detection of 4.42ngmL−1. The prepared MMIPs could be employed to selectively pre-concentrate and determine resveratrol from wine samples.
We discover new types of quantum anomalies in two-dimensional systems with time-reversal symmetry (
) and discrete rotation symmetry with order of
= 2, 4, and 6 (
). The new anomalous states have
...flavors of massless Dirac fermions protected by
and
, whereas any two-dimensional lattices having the two symmetries must have a multiple of 4, 8, and 12 Dirac cones for
= 2, 4, and 6, respectively. We show that these anomalous states are physically realized on the surface of new classes of topological crystalline insulators, normal to the rotation axis. Moreover, these topological crystalline insulators support
gapless one-dimensional helical mode on the otherwise fully gapped side surface, connecting the anomalous two-dimensional states on the top and bottom surfaces. The presence of these helical modes enables a new quantum device made from a topological crystalline insulator nanorod, a "helical nanorod," which has a quantized longitudinal conductance of
/
.
The structure property is the fundamental factor in determining the stability, adsorption, catalytic performance, and selectivity of microporous materials. Seven density functional approximations ...(DFAs) are used to simulate the crystal structure of microporous material for examining the efficiency and accuracy. In comparison with the existing zeolites, microporous materials with CHA framework are selected as the testing model. The calculation results indicate that the least lattice volume deviation is 5.18/2.72 Å3 from PBE_mGGA, and the second least is −5.55/−10.36 Å3 from LDA_PP. Contrary to USPP_LDA, PBE_GW, PAW_PBE, and PAW_GGA overestimate the lattice volume by ~15.00–20.00 Å3. For each method, RMS deviations are less than 0.016 Å for bond length and less than 2.813° for bond angle. To complete the crystal structure calculation, the CPU time reduces in order of USPP_GGA > PBE_GW > PAW_GGA, PBE_mGGA > PAW_PBE > LDA_PP > USPP_LDA. For two testing models, when the calculation time is not important, PBE_mGGA is the best choice, and when the tradeoff between accuracy and efficiency is considered, LDA_PP is preferred. It seems feasible and efficient to simulate the zeolite structure through E-V curve fitting, full optimization, and phonon analysis bythe periodic density functional theory.
Abstract
Dual-energy X-ray absorptiometry (DXA) is underutilized to measure bone mineral density (BMD) and evaluate fracture risk. We present an automated tool to identify fractures, predict BMD, and ...evaluate fracture risk using plain radiographs. The tool performance is evaluated on 5164 and 18175 patients with pelvis/lumbar spine radiographs and Hologic DXA. The model is well calibrated with minimal bias in the hip (slope = 0.982, calibration-in-the-large = −0.003) and the lumbar spine BMD (slope = 0.978, calibration-in-the-large = 0.003). The area under the precision-recall curve and accuracy are 0.89 and 91.7% for hip osteoporosis, 0.89 and 86.2% for spine osteoporosis, 0.83 and 95.0% for high 10-year major fracture risk, and 0.96 and 90.0% for high hip fracture risk. The tool classifies 5206 (84.8%) patients with 95% positive or negative predictive value for osteoporosis, compared to 3008 DXA conducted at the same study period. This automated tool may help identify high-risk patients for osteoporosis.
High‐quality perovskite monocrystalline films are successfully grown through cavitation‐triggered asymmetric crystallization. These films enable a simple cell structure, ITO/CH3NH3PbBr3/Au, with near ...100% internal quantum efficiency, promising power conversion efficiencies (PCEs) >5%, and superior stability for prototype cells. Furthermore, the monocrystalline devices using a hole‐transporter‐free structure yield PCEs ≈6.5%, the highest among other similar‐structured CH3NH3PbBr3 solar cells to date.
To clarify the epidemiological, clinical, and therapeutic features of patients with severe COVID-19.
In this study, we enrolled 681 patients with confirmed cases of severe COVID-19. The ...epidemiological, demographic, clinical, laboratory, treatment, and outcome data were collected.
The median age of the study participants was 65 years, 53.2% were male, and 104 (15.3%) died. Age, Neutrophil-To-Lymphocyte Ratio (NLR), acute myocardial injury, and levels of C-reactive protein (CRP), lactate dehydrogenase (LDH), and CD3 T cells counts were independently associated with death, while arbidol and ribavirin were protective from death. The combination of NLR and acute myocardial injury on admission (AUC = 0.914) predicted mortality better than NLR, CRP, LDH, and acute myocardial injury. There were 312 (45.8%) patients with cardiovascular disease, of whom 23.4% died. β-blockers, ACEI/ARB, arbidol, and ribavirin might have a beneficial effect for severe COVID-19 patients with cardiovascular disease.
The combination of NLR and acute myocardial injury on admission was highly predictive of mortality and survival. Clinicians should adopt more aggressive strategies for patients with a high NLR (>6.66) combined with myocardial injury. β-blockers and ACEI/ARB, as well as arbidol and ribavirin, were effective in COVID-19 patients with cardiovascular disease.
•Combination of NLR and acute myocardial injury could predict mortality.•Patients combined with higher NLR and myocardial injury need aggressive strategies.•Arbidol and ribavirin may be benefit to severe COVID-19.•β-blockers and ACEI/ARB are effective for patients with cardiovascular disease.
Prompt recombination of photogenerated electrons and holes in bulk and on the surface of photocatalysts harshly impedes the photocatalytic efficiency. However, the simultaneous manipulation of ...photocharges in the two locations is challenging. Herein, the synchronous promotion of bulk and surface separation of photoinduced charges for prominent CO2 photoreduction by coupling macroscopic spontaneous polarization and surface oxygen vacancies (OVs) of BiOIO3 single crystals is reported. The oriented growth of BiOIO3 single‐crystal nanostrips along the 001 direction, ensuing substantial well‐aligned IO3 polar units, renders a large enhancement for the macroscopic polarization electric field, which is capable of driving the rapid separation and migration of charges from bulk to surface. Meanwhile the introduction of surface OVs establishes a local electric field for charge migration to catalytic sites on the surface of BiOIO3 nanostrips. Highly polarized BiOIO3 nanostrips with ample OVs demonstrate outstanding CO2 reduction activity for CO production with a rate of 17.33 µmol g−1 h−1 (approximately ten times enhancement) without any sacrificial agents or cocatalysts, being one of the best CO2 reduction photocatalysts in the gas–solid system reported so far. This work provides an integrated solution to governing charge movement behavior on the basis of collaborative polarization from bulk and surface.
Collaborative polarization by macroscopic spontaneous polarization and surface oxygen vacancies induces efficient bulk and surface charge separation of BiOIO3 nanostrips, which gives rise to extraordinary CO2 photoreduction activity with a CO evolution rate of 17.33 µmol g−1 h−1, over ten times that of BiOIO3 nanoparticles, also outperforming most previously reported high‐performance photocatalysts.
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